Regarding a disc brake for braking a vehicle such as automobile, a floating disc brake has been widely known and has been actually used which supports a caliper so that it can displace in an axial direction (in the specification and the claims, an ‘axial direction’, a ‘diametrical direction’ and a ‘circumferential direction’ means an ‘axial direction’, a ‘diametrical direction’ and a ‘circumferential direction’ of a rotor, respectively) with respect to a support.
FIG. 57 shows a floating disc brake, which is a first example of the prior art disclosed in PTL1. The floating disc brake displaces a caliper 2 with respect to a rotor 1 rotating together with a wheel (not shown), upon braking. At a state where the brake is mounted to a vehicle, a support 3 that is provided in the vicinity of one side of the rotor 1 in an axial direction is fixed to a vehicle body (not shown). Also, the caliper 2 is supported to the support 3 so as to be axially displaceable.
Therefore, a pair of guide pins 4 that is provided at both end portions of the caliper 2 in a circumferential direction and a pair of guide holes 5 that is provided at both end portions of the support 3 in a circumferential direction are provided in parallel with a central axis of the rotor 1, respectively. The guide pins 4 are axially slidably inserted into the guide holes 5. Boots 6, 6, for dust-proof are provided between outer peripheries of base end portions of the guide pins 4 and openings of the guide holes 5.
Also, at both end portions of the support 3, rotation input side and rotation output side engaging sections 7, 8 are respectively provided at parts spaced from the rotor 1 in the circumferential direction. Both circumferential end portions of pressure plates 10a, 10b configuring pads 9a, 9b are engaged with the engaging sections 7, 8. Also, the caliper 2 having a cylinder section 11 and a claw section 12 is arranged so that it extends over the both the pads 9a, 9b. Also, the cylinder section 11 is fluid-tightly fitted with a piston 13 that presses the inner (upper side in FIG. 57 at a widthwise inner side of the vehicle) pad 9a to the rotor 1.
When braking the vehicle, a pressure oil is supplied into the cylinder section 11, so that a lining 14a of the inner pad 9a is pressed to an inner surface of the rotor 1 from the upper to the lower in FIG. 57 by the piston 13. Thus, as a reaction to the pressing force, the caliper 2 is displaced upward in FIG. 57, based on the sliding between the guide pins 4 and the guide holes 5, and the claw section 12 presses a lining 14b of the outer (lower side in FIG. 57 at a widthwise outer side of the vehicle) pad 9b to an outer surface of the rotor 1. As a result, the rotor 1 is strongly held from both inner and outer side surfaces, so that the braking is made.
Upon the non-braking of the disc brake configured and operating as described above, when the linings 14a, 14b of the respective pads 9a, 9b and the inner and outer side surfaces of the rotor 1 rub each other, drag torque (rotation resistance) of the rotor 1 is increased, so that the gas mileage performance is lowered and the linings 14a, 14b are unnecessarily worn. The unnecessary wear of the linings 14a, 14b lowers a mileage until the respective pads 9a, 9b are replaced, so that the driving cost is increased.
In order to solve the above problem, for example, PTLs 2 to 4 disclose a structure where a return spring is provided between the inner and outer pads and friction surfaces of the linings of the pads are separated from both side surfaces of the rotor as the braking is released. FIG. 58 shows a second example of the prior art disclosed in PTL2.
In the second example, between the support 3 and the pads 9a, 9b, a pad clip 15 for preventing the pads 9a, 9b from rattling is provided and a return spring 16 for applying an elastic urging force (returning force) to the pads 9a, 9b in a direction getting away from each other is provided. The return spring 16 has a substantial M shape that is a whole shape, and has a coil section 17 at a central portion thereof in an axial direction. Both end portions of the return spring 16 are engaged into engaging holes 18, 18 that are formed on outer peripheral edges of circumferential end portions of the pressure plates 10a, 10b, and the coil section 17 is engaged to a protruding pin 19 extending from an upper end edge of the pad clip 15. By the configuration as described above, the elastic urging force is applied to the pads 9a, 9b in the direction getting away from each other. Hence, upon the braking release, friction surfaces of the linings 14a, 14b of the pads 9a, 9b are separated from both side surfaces of the rotor 1.
In the second example of the prior art, upon the non-braking, it is possible to prevent the friction between the linings 14a, 14b of the pads 9a, 9b and the side surfaces of the rotor. However, the assembling operation is troublesome and the assembling cost is thus increased. That is, in the second example, it is not possible to support the return spring 16 to the pad clip 15 with sufficient support force. Hence, when mounting the pad clip 15, it is not possible to handle the pad clip 15 and the return spring 16 as an integral article, so that it is necessary to separately perform the mounting operations. Also, just after mounting the return spring 16, the elastic urging force is applied to the pads 9a, 9b in the direction getting away from each other. Hence, it is necessary to configure the pads 9a, 9b so that they are not separated and deviated from the support 3 in the axial direction. Also, even when separating the caliper upon the replace of the pads 9a, 9b, since the elastic urging force of the return spring 16 is being applied to the respective pads 9a, 9b, it is necessary to configure the respective pads 9a, 9b so that they are not separated. Such assembling operation or replacing operation is troublesome, so that the assembling cost is increased.
Also, in the second example, both end portions of the return spring 16 are engaged to the outer peripheral edges of the respective pads 9a, 9b. Hence, at a state where the braking is released, the pads 9a, 9b are more apt to be inclined in a direction coming close to the rotor at the inner diameter sides (inner peripheral edges). Therefore, the side surfaces of the rotor and the inner peripheral edges of the linings 14a, 14b of the pads 9a, 9b easily rub each other.
Also, the magnitudes of the elastic urging force applied to the pads 9a, 9b by the return spring 16 are the same. Therefore, an amount of wear of the lining 14b of the outer pad 9b of the pads 9a, 9b may be larger than that of the lining 14a of the inner pad 9a. That is, upon the braking release, the supply of the pressure oil into the cylinder section is stopped, so that the force of pressing the inner pad 9a toward the rotor is lost. Therefore, the inner pad 9a can be relatively easily displaced in a direction getting away from the inner side surface of the rotor. Compared to this, while the outer pad 9b is displaced in a direction getting away from the outer side surface of the rotor, the friction (for example, sliding friction to be applied between the guide pin and the guide hole) that is applied to the sliding section of the caliper acts as resistance. Accordingly, the outer pad 9b is difficult to be displaced in a direction getting away from the outer side surface of the rotor. As a result, as described above, an amount of wear of the lining 14b of the outer pad 9b may be larger than that of the lining 14a of the inner pad 9a. Also, a thickness of the rotor may be varied due to the wear, which causes judder.
PTLs 2 to 4 do not describe or suggest a configuration for solving the above problems.
Also, as shown in FIG. 59, PTL5 discloses a structure where a return spring 56, which is formed by bending a wire rod and has a pair of coil sections 55, 55 at a central portion thereof, is engaged to an anti-rattle spring 57. In the structure disclosed in PTL5, each of the coil sections 55, 55 is provided so that a direction of a central axis and a diametrical direction are substantially matched. Therefore, as the coil sections 55, 55 are put on, a size of the support 3 in a circumferential direction is increased, so that it is difficult to secure a gap between the support 3 and an inner periphery of a wheel (not shown), regarding a layout. Also, outer end portions of the pads 9a, 9b in the diametrical direction are pressed by pressing sections (engaging sections) 58, 58 provided to the return spring 56. Thereby, as the braking is released, the diametrically outer sides are widened each other, i.e., the pads 9a, 9b are easily fallen. Even when it is intended to press the diametrically central portions of the respective pads 9a, 9b, a length (whole length) from each of the coil sections 55, 55 to each of the pressing sections 58, 58 is lengthened and the coil sections 55, 55 and the pressing sections 58, 58 are largely deviated in the diametrical direction (a diametrical length is increased). Hence, it is not possible to effectively use the elastic deformation of the coil sections 55, 55 as the returning force of separating the pads 9a, 9b from the rotor. Also, in the structure disclosed in PTL5, after the anti-rattle spring 57 is mounted to the support 3 and the respective pads 9a, 9b are then mounted thereto, the return spring 56 is simply mounted. That is, PTL5 does not consider at all that the return spring 56 is mounted to the anti-rattle spring 57 before the respective pads 9a, 9b are mounted and that the anti-rattle spring 57 and the return spring 56 are handled as an integral article (assembly).